So Okay, It's Average: While the game is largely considered to at least be free of any truly severe glitches and generally not an atrocious game overall, the fact that it barely adds anything new to the kart racer table while also being very lazy with its use of the Nickelodeon license and its many IPs (of which only four are represented in-game, resulting in only 12 playable characters) makes for a very unexciting and homogeneous gaming experience.
Tainted by the Preview: The roster being revealed to only have 12 characters did not go over well, considering that it was originally reported that the game would have 12 franchises - rather than merely 12 characters - represented. On top of that, these 12 characters are only taken from four Nicktoon series (3 of which were represented in previous entries in the series) out of the dozens that were around at the time of the game's release, which is often considered a huge waste of the Nickelodeon license.
They Wasted a Perfectly Good Plot: The fact that the game chooses to only have twelve characters from only four Nicktoons and draw tracks only from said four Nicktoons in a Nickelodeon crossover kart racer in 2018 (when there are now plenty of Nicktoons to draw characters from compared to the handful of Nicktoons that there were when Nicktoons Racing was released back in 2000) is just considered such a huge waste of the extensive and versatile Nickelodeon license. Not even Nicktoons that were incredibly popular and/or still running at the time the game was released such as The Loud House were included, nor were ones that were never featured in any of the previous Nickelodeon racing games such as My Life as a Teenage Robot and Rocko's Modern Life. Fortunately, the sequel includes a much wider array of Nicktoons represented.
Unexpected Character: While Tommy and Angelica were obvious choices for playable Rugrats representation, not many expected Reptar to make the cut as well, and over more prominent characters like Chuckie (who wouldn't be added until the game's sequel), Phil, Lil, or Kimi to bootnote Phil and Lil do make a cameo in one of the Rugrats tracks.
Tropes for Nickelodeon Kart Racers 2: Grand Prix:
Author's Saving Throw: More than doubling the first game's extremely paltry roster, including characters from shows not represented in the original, such as The Loud House and Invader Zim, as well as including many new features helped to inspire faith in the sequel.
While Lincoln and Lucy were obvious choices for The Loud House representatives, Clyde came out of left field considering his lesser prominence compared to the Louds themselves and his divisive status within the fanbase.
Some were surprised that Ren & Stimpy are in the game, especially in light of the sexual abuse allegations against John Kricfalusi that resulted in Nickelodeon temporarily pulling reruns and merchandise of the show. However, both characters appearing in the original Nicktoons Racing does mitigate this quite a bit.